I've been trying out the threeme3/WsprryPi source that cleverly turns a Raspberry Pi into a little WSPR beacon. It really works! Here's my in-house big power transmitting station:
Here's the command line I used to transmit, pause twice, and transmit:
So, note that the arguments to ./wspr are call locator dBm freq freq freq...
To pause you put a zero for a frequency. And here's how it looks on a local WSPR receiver:
While there is some spurious signals there, it's basically quite stable and on time (that last one ended early because I killed it).
Mine was 1.4KHz below frequency and to get it close to 14,097100 (mid wspr band) I had to tell it to transmit on 14,095700.
Later when band conditions improve I'll connect it to an antenna and see how we go.